The present invention generally relates to a piping system and, more particularly, to an improvement in a piping connection between an exhaust port of an internal combustion engine and an intake port of a thermal reactor for substantially purifying exhaust gases emitted from the combustion engine.
In some conventional combustion engines used, for example, on automotive vehicles, an exhaust gas purifying device, such as a thermal reactor for reburning noxious, residual combustibles present in the exhaust gases to substantially purify the latter, is installed in the exhaust system of the engine. Because of the nature and construction of the thermal reactor which is well known to those skilled in the art, reduction of the temperature of the exhaust gases prior to said exhaust gases entering the thermal reactor does not ensure an efficient and effective re-combustion of the residual combustibles in the exhaust gases within the thermal reactor.
In order to avoid the undesirable reduction of the temperature of the exhaust gases introduced into the thermal reactor, various methods have heretofore been employed. One of these methods is the use of a tubular insert installed within an exhaust passage leading from the combustion chamber to the exhaust port, such as disclosed in U.S. patent application Ser. No. 607,822, filed on Aug. 25, 1975 now U.S. Pat. No. 3,984,977 and assigned to the same assignee of the present invention.
According to U.S. patent application Ser. No. 607,822, the tubular insert extends from a plane of the opening of the exhaust port into the exhaust passage and is supported in position in spaced relation to the wall of the engine block or casing which surrounds the exhaust passage by means of a heat insulating member of a substantially ring shape. By the interposition of the heat insulating member or ring, dissipation of the heat evolved in the tubular insert in contact with the exhaust gases flowing therethrough, which may take place due to contact with the generally forcibly cooled engine block, is advantageously minimized. Moreover, that end of the tubular insert flush with the opening of the exhaust port is radially outwardly flanged and is in turn restrained by one or more set pins extending through a portion of the engine block into the flanged end of the tubular insert in a direction perpendicular to the longitudinal axis of the tubular insert, for avoiding relative rotation of the tubular insert and also for avoiding possible separation of the tubular insert from the exhaust passage.
Another method is the provision of a plurality of areas of reduced surface contact in the radially outwardly extending flange rigid or integral with one end of an intake pipe leading into a reaction chamber of the thermal reactor, such as disclosed in U.S. patent application Ser. No. 579,076, filed on May 19, 1975 now U.S. Pat. No. 4,013,098 and assigned to the same assignee of the present invention. The reduced surface contact areas in the flange at one end of the intake pipe are, according to U.S. patent application Ser. No. 579,076, constituted either by arcuate slots arranged in a circular configuration in equally spaced relation to each other or by radially outwardly extending segments defined in the flange by cutting the latter inwards towards the intake pipe at spaced intervals around the circumference of the flange. These reduced surface contact areas, that is, any of the arcuate slots and the cut-out portions each defined between adjacent radially outwardly extending segments in the flange, serve to minimize the undesirable transmission of heat from the intake pipe to the engine block or an outer shell or casing of the thermal reactor by way of the flange at the end of the intake pipe.
The aforesaid methods to avoid the undesirable reduction of the temperature of the exhaust gases to be introduced into the thermal reactor are individually directed to the exhaust port arrangement in the combustion engine and to the intake pipe construction in the thermal reactor, respectively. However, even if a thermal reactor having a intake pipe constructed according to the second mentioned U.S. patent application is provided on an engine having the exhaust port constructed according to the first mentioned U.S. patent application, there is still a drawback in that a difference in temperature tends to be created between the tubular insert within the exhaust passage and the intake pipe within the thermal reactor because of the presence of a clearance between the flanged end of the intake pipe in the thermal reactor and the flanged end of the tubular insert within the exhaust passage in the engine block.
On the other hand, U.S. Pat. No. 3,635,031, patented on Jan. 18, 1972, discloses the use of a single piping element connecting either one of the exhaust port in the engine block and the intake port in the thermal reactor to the other of the exhaust port and the intake port and having one end situated within the exhaust passage in the engine block and the other end situated within the thermal reactor and connected to an opening in an inner shell defining the reaction chamber. The employment of the single piping element is advantageous in that the temperature at the end of the piping element adjacent the reaction chamber can readily be transmitted to the opposite end of the piping element adjacent the combustion chamber of the combustion engine, thereby causing the piping element to be kept heated by the elevated temperature prevailing within the reaction chamber of the thermal reactor.
Although the single piping element functions satisfactorily, mounting of the thermal reactor on the combustion engine is complicated and time-consuming.